1. Field of the Invention
The present invention relates to a brake disk, more particularly to a brake disk which brake pads are pressed against for braking.
2. Background Art
A conventional disk brake for a motorcycle has a brake disk and brake pads which are pressed against the opposite surfaces (friction members) of the brake disk for braking. Some lightweight brake disks have disk bodies formed of a lightweight material, and friction members of a highly frictional material are attached to the opposite surfaces of their respective disk body.
An exemplary disk brake disclosed in Japanese Application No. JP-A No. H8-226478 has a lightweight brake disk as aforementioned. Friction parts are formed in this type of arrangement by fixing frictional material to the opposite surfaces of the disk body of the brake disk. The formation of the friction parts with frictional material enables the formation of a lightweight brake disk from a light aluminum alloy.
However, some types of brake disks need friction parts requiring a greater thickness. Another exemplary brake disk of the conventional art is disclosed in Japanese Patent Application No. JP-A No. H9-42339. This type of brake disk is provided with thick frictional members. This type of arrangement bonds friction members formed from an alloy steel to the opposite surfaces of an aluminum disk by explosive cladding.
However explosive cladding is an expensive, complex and time consuming process. Explosive cladding processes require the troublesome steps of putting an alloy steel member on an aluminum member, mounting a buffer on the alloy steel member, putting a proper amount of explosive on the buffer, and detonating the explosive by a detonator attached to one end of the explosive.
An exemplary disk rotor of the conventional art is disclosed in Japanese Utility Model No. 2557898. In this type of arrangement, a brake disk is provided with a thick frictional member. This arrangement incorporates a plate-shaped member of a carbon-fiber-reinforced composite material positioned between a pair of metal plates forming a disk rotor. The pair of metal plates and the plate-shaped member are joined together by riveting.
However, a process for uniting together the pair of metal plates and the plate-shaped member requires a step of forming a plurality of through holes in the pair of metal plates and the plate-shaped member, and an additional step of pressing down the ends of a plurality of rivets. Thus, this technique requires additional parts, additional fabrication steps and ultimately increased manufacturing/assembly costs.
The conventional art arrangements are not practically suited for mass production in which a member formed of a titanium alloy or an aluminum alloy and member formed of an iron-base material are bonded together.
The explosive cladding method proposed in JP-A No. H9-42339 and the rivet bonding method disclosed in Japanese Utility Model No. 2557898 increase the manufacturing costs of the brake disk. Accordingly, manufacturing techniques that will replace these known techniques would be advantageous to the related art.
The present invention overcomes the shortcomings associated with the related art and achieves other advantages not realized by the related art.
An aspect of the present invention to provide techniques capable of reducing the weight of a brake disk by bonding together a member of a titanium alloy or an aluminum alloy, and a member formed of an iron-base member.
An additional aspect of the present invention is to provide an inexpensive disk brake.
These and other aspects are accomplished by a brake disk comprising a disk body formed of a titanium alloy or an aluminum alloy; and friction members formed of an iron-based material and bonded to opposite surfaces of the disk body by brazing.
These and other aspects are further accomplished by a brake disk for mounting on a hub included in a wheel of a motorcycle, the brake disk comprising a disk body formed of a titanium alloy or an aluminum alloy, the disk body having an inner surface and an outer surface; and a pair of friction members formed of an iron-base material and bonded to the inner surface and the outer surface of the disk body by a respective brazing layer; wherein the pair of friction members has an inner friction member and an outer friction member, the inner friction member having a thickness t3 different from a thickness t5 of the outer friction member.
These and other aspects are further accomplished by a method of forming a brake disk, the method comprising the steps of positioning a first friction member between a plurality of pins attached to a support plate of a jig; applying a first brazing metal filler layer to the first friction member; positioning a first surface of a disk body over the brazing metal filler layer; applying a second brazing metal filler layer on a second surface of the disk body; positioning a second friction member over the second brazing metal layer; applying a pressure plate onto the second friction member; placing the jig holding the first and second friction members, support plate, first and second brazing metal filler layers, and disk body in a vacuum vessel; applying a load to the pressure plate; and heating an interior atmosphere of the vacuum vessel to a predetermined brazing metal activation temperature for a predetermined period of time.
In order to achieve the aforementioned objects, a brake disk stated in a first aspect of the invention comprises a disk body formed of a titanium alloy or an aluminum alloy, and friction members formed of an iron-base material and bonded to the opposite surfaces of the disk body by brazing.
Prior to the present invention, there has not been any practical technique suitable for mass production of disk brakes including a member of a light titanium alloy or aluminum alloy having a high strength, and a member of an iron-base material. According to the present invention, the disk body is formed of a light titanium alloy or aluminum alloy having a high strength, and friction members formed of an iron-base material are bonded together by brazing. The use of a light titanium alloy or aluminum alloys having a high strength reduces the weight of the brake disk.
The friction members are bonded to the disk body by brazing. The friction members can be bonded to the disk body simply by forming a brazing filler metal layer between each of the friction members and the disk body and melting the brazing filler metal layer.
As is generally known, when a brake disk is incorporated into a motorcycle, the outer surface of the brake disk opposite the inner surface of the same facing the wheel of the motorcycle is exposed more efficiently to running wind than the inner surface. Therefore, when a braking force is exerted on the brake disk, the inner friction member facing the wheel is heated at a temperature higher than that at which the outer friction member is heated. In addition, friction coefficient between the friction member and a brake pad decreases as the temperature of the friction member rises. Therefore, it is important to maintain the friction members at a fixed temperature.
Moreover, the pair of friction members are formed having respectively different thicknesses. The thicker friction member is bonded to the inner surface of the disk body facing the wheel and the thinner friction member is bonded to the outer surface of the disk body. The thicker friction member bonded to the inner surface of the disk body on the side of the wheel is capable of absorbing a large amount of heat generated when a braking force is applied to the brake disk. Thus, the inner friction member facing the wheel and the outer friction member not facing the wheel can be maintained at substantially the same temperature. Consequently, the disk body is capable of absorbing a large amount of heat generated when a braking force is applied to the brake disk.
Thus, the inner friction member facing the wheel and the outer friction member facing away from the wheel are maintained at the same relative temperature. Consequently, both the friction coefficient associated with the inner friction member and the friction coefficient associated with the outer friction member can be held on a substantially fixed level.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.